DISPLAYABLE CHARACTER SETS FOR BROADCAST TELETEXT Tech. 3232-E Second edition - June 1982 CONTENTS 1 Introduction........................................................................................................................................3 2. EBU inquiry....................................................................................................................................4 3. Analysis of the replies from EBU members...................................................................................4 3.1 Minimum number of characters required ..................................................................................4 3.2 Two or more languages on one page .......................................................................................6 4. Establishment of multilingual character repertoires.......................................................................8 4.1 Constraints that have to be taken into account.........................................................................8 4.2 Significance of the repertoires ..................................................................................................8 4.3 Character repertoires for languages written in Latin-based-alphabets.....................................9 4.4 The combination of non-Latin-based alphabets together with a limited selection of Latin- based characters - ..................................................................................................................11 5. Conclusion ...................................................................................................................................14 Bibliographical references ......................................................................................................................15 Appendix 1- Example of the forms used in the EBU inquiry .............................................................17 Appendix 2- The complete repertoire of Latin-based characters required by EBU Member- organisations ................................................................................................................18 Appendix 3- Generation of the characters of the ASV-CODAR/I set by means of a 5 x 9 dot matrix. ...........................................................................................................20 Appendix 4- Coding table for a combined repertoire of ASV-CODAR/I and certain Latin-based characters. ...................................................................................................................21 Appendix 5- Provisional proposed combined repertoire for the Arabic alphabet. ............................22 Appendix 6- Provisional proposed combined repertoire for the Cyrillic alphabet ............................23 Appendix 7- Provisional proposed combined repertoire for the Greek alphabet .. ...........................24 Appendix 8- Provisional proposed combined repertoire for the Hebrew alphabet ..........................25 Appendix 9- Generation of the characters specific to Hebrew and the figures of Indian origin, in 5 x 9 dot matrix. ........................................................................................................26 Technical Centre of the European Broadcasting Union Avenue Albert Lancaster 32, B-ll8O Bruxelles (Belgium) 2 Displayable character sets for broadcast teletext EBU Tech 3232 Following the preparation of the first edition of this document, in 1980, information has been obtained on certain additional aspects of the requirements of EBU Member-organisations, and this has been taken into account in preparing this second edition. The complete Latin-based repertoire has been revised, and proposals are given for four "combined repertoires", each consisting of a combination of the characters required for the display of the seven languages most widely used in Western Europe with those required for the display of texts in one of the following non- Latin-based alphabets: Arabic, Cyrillic, Greek and Hebrew. As a number of amendments to the original text have been made also, this text should be considered to replace that of the first edition. EBU Tech 3232: Displayable character sets for broadcast teletext 3 DISPLAYABLE CHARACTER SETS FOR BROADCAST TELETEXT 1 Introduction The topic of data transmission systems in broadcasting has been attracting more and more attention during the past few years, and the Bureau of the EBU Technical Committee decided, at its meeting in October 1976, that an Ad-hoc group should be formed to study the characteristics of such systems and, in the case of teletext, the possibilities of defining a standard European alphabet and of drafting the specifications of a universal receiving terminal. The character sets employed by the teletext services that have already been introduced were derived from the set standardised by the ISO and CCITT for professional data-processing, by the addition and replacement of a few special characters. However, experience has shown that these sets are in general inadequate and inefficient for applications in domestic teletext broadcasting. On the one hand, public acceptance of this new medium of communication requires a character set at least as extensive as that customary on typewriters intended for the languages concerned, and on the other hand the limited number of characters that can be displayed on a single "page" makes it necessary to be able to use as many abbreviations and symbols as possible. Because no reliable information was available on the precise desires of the EBU Member-organisations in this field, the Ad-hoc Group, which has since become known as Sub-group V2, therefore undertook a survey of their minimum requirements regarding character repertoires for use in domestic data broadcasting services. The survey was organised in such a way that information could be obtained on both the total set of characters from which it was desired that any page of text could be composed, and the sets of characters specific to each language, so that the requirements for different combinations of languages could be derived. This document consists of an analysis of the replies received in response to the survey, together with proposals for various sets of displayable characters, known as repertoires, complying with the requirements expressed by EBU Member-organisations. It is intended that this information should provide the basis for international standardisation in the field of teletext broadcasting. 4 Displayable character sets for broadcast teletext EBU Tech 3232 2. EBU inquiry At the end of 1978, the EBU undertook a survey of the requirements of its Members in the field of character sets for broadcast teletext. In order to facilitate the analysis of the replies, respondents were asked to indicate, for each language likely to be required for teletext, the minimum character set necessary, together with what other languages were likely to be required on the same page. The replies were to be entered on a form containing two tables, each of which was subdivided into eight different types of character. One table already contained the proposed basic character set (consisting of all the characters common to the character sets initially specified for U.K. teletext and Antiope), and the other already contained examples of the additional characters required for one of four geographically-related groups of languages. Examples of the forms used are reproduced in Appendix 1. The respondents were asked to delete all redundant characters in both tables, and to insert any additional characters required in the second table, so that the contents of both tables taken together would represent the minimum set required for the language under consideration. 3. Analysis of the replies from EBU members A very large response was obtained; nearly all EBU Active Members returned completed forms, and several of them also provided explanations of the reasons for which their choice was made. As in some cases several different organisations provided information regarding the same language. it is also possible to obtain some idea of the degree of flexibility in the requirements. 3.1 Minimum number of characters required Table 1 shows the total minimum number of characters required for each language by each broadcasting organisation, and how many are included in the "basic" and "additional" categories. It can be seen that each of the Northern European languages and Turkish require a total of no more than approximately 96 characters (except in the cases of Dutch and Norwegian, which are discussed below). On the other hand, the Romance languages (French, Italian, Spanish and Portuguese) all require substantially more than 96 characters, generally between 110 and 127; the exceptionally large requirements of Italian (RAI) are due to the inclusion of characters which are taken from other alphabets or are restricted to particular applications. It should be noted that the information about Spanish given in Table 1 (but not elsewhere) corresponds to the combined requirements for Basque, Catalan, Galician and Spanish. Finally, so far as languages written in non-Latin-based alphabets are concerned, whereas Arabic requires a total of less than 96 characters, Greek requires 127 characters if all accented characters, and the accents themselves, are to be included. EBU Tech 3232: Displayable character sets for broadcast teletext 5 Table 1.- Summary of the essential requirements for character sets Referen Language Organisation Other languages requested on No. of characters